The present invention relates to a method for fitting a tubular roll mantle of a roll intended for a paper machine or equivalent with glide bearings, in which the roll mantle is supported on a stationary roll axle by means of hydraulic glide-bearing members acting upon the roll mantle or upon the roll ends. The bearing members are hydraulically loaded by the effective pressure applied by of a pressure medium.
Further, the invention relates to a method for fitting a tubular roll mantle of a roll intended for a paper machine or equivalent with glide bearings, in which the roll mantle is supported on a stationary roll axle by hydraulic glide-bearing members acting upon the roll mantle or upon the roll ends. The bearing members are hydraulically loaded by means of a pressure medium, while the roll is loaded radially in the direction of at least one plane, i.e., in the so-called main loading direction.
Further, the invention relates to a tubular roll that makes use of the method for a paper machine or equivalent. The roll mantle of the roll is revolvingly supported on a stationary roll axle by means of glide-bearing members that act upon the inner face of the roll mantle and/or upon the roll ends. The glide-bearing members are loaded by means of the effective pressure of a hydraulic pressure medium.
The invention also relates to a tubular roll that makes use of the method in accordance with the invention for a paper machine or equivalent. The roll mantle of the roll is revolvingly supported on a stationary roll axle by means of glide-bearing members that act upon the inner face of the roll mantle and/or upon the roll ends. The glide-bearing members are loaded by means of the pressure of a hydraulic pressure medium, while the roll is loaded radially in the direction of at least one plane, i.e., in the so-called main loading direction.
Tubular rolls in paper machines are ordinarily mounted or journalled on the roll axle at the ends of the roll mantle by means of roller bearings. Such a conventional mode of journalling has its advantages, for example, the fact that the journalling can be accomplished quite simply, and so far its costs have been considered to be relatively moderate. However, this conventional mode of journalling, in which the roll mantle is journalled on the axle permanently by its ends, is not suitable for all objects of use in paper machines. In quite a number of cases, the roll mantle must be able to move radially in relation to the roll axle, which characteristic is quite often required, e.g., for variable-crown rolls which are in nip contact with a back-up roll. By means of the crown variation means in a variable-crown roll, attempts are made to shape the roll mantle in the desired way especially in view of regulation of the profile of linear load. Therefore, the roll ends must also be able to move in the radial direction in relation to the axle in order that the profile of linear load could be controlled in the end areas of the roll. In addition to the profile-regulation properties in the end areas of the roll, the regulation of the loading in the end areas of the roll also affects the control of the temperatures in the end areas of the roll.
For this reason, such rolls have been developed in which the entire roll mantle can move in the direction of loading radially in relation to the roll axle. One roll of this type is described in the assignee's EP Patent No. 0 332 594. In the roll described in this reference, the end bearings of the variable-crown roll are not mounted directly on the central axle of the roll. Rather, the bearings are arranged on separate annular parts which can move radially in relation to the roll axle. The variable-crown roll in accordance with this reference is a nip roll, and the radial movement of the roll mantle is confined to the direction of the nip plane. The movement is accomplished so that hydraulic power units are arranged between the annular parts and the roll axle. The power units shift the end bearings by means of a hydraulic pressure medium toward the nip or away from the nip. The principal object of the device in EP '594 of this solution is to open and close the nip. There is also a large number of other rolls of similar type, which produce a substantially corresponding action accomplished by means of a somewhat different technique.
The fitting of a roll with roller bearings also produces considerable drawbacks and/or problems for the manufacture and operation of the roll. It is one particular drawback that the roller bearings require certain machining of the roll mantle. The wear of the bearings may also result in problems and, further, the roller bearings impose their restrictions in respect of the oil or fluid to be used in the roll. For example, the following properties can be considered as the weak points of the conventional mode of journalling.
Restrictions of speed: Even at present, the speeds of rotation of the rolls exceed the maximum permitted speeds specified by bearing manufacturers.
Precision of rolling: With the present technology, it is very difficult to increase the rolling precision of an assembled roll further. In a traditional roll, even if all the components (bearings, bearing spaces, outer face of mantle) are machined as precisely as possible, the defects are summed up in an assembled roll.
Fitting of a roll mantle with glide bearings is also known in the prior art. One such roll with glide bearings is described in U.S. Pat. No. 5,111,563. By means of the device shown in this reference, the object has been to provide a roll which automatically corrects and compensates for the loading of the roll. However, a significant drawback of this device is its highly complicated construction, as a result of which the controllability of the operation is not as good as possible.